The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for forming a magnetic tunnel junction (MTJ) cell.
Recently, as semiconductor devices become highly integrated, magnetic random access memory (MRAM) has attracted a good deal of attention as a next generation high performance non-volatile semiconductor memory device. The MRAM includes a transistor performing a switching operation, and an MTJ cell for storing data. The MTJ cell includes a magnetic tunnel junction unit having a dielectric layer interposed between two ferromagnetic layers. The electric resistance of the MTJ cell is changed in according to a magnetization orientation of the two ferromagnetic layers. Using a voltage change or a current change according to the resistance change, it can be determined which logic level (“1” or “0”) the data stored in the MTJ cell has.
FIG. 1 illustrates a cross-sectional view of a typical MTJ cell on which an etch byproduct is deposited. FIG. 2 illustrates a micrographic view of a typical MTJ cell on which an etch byproduct is deposited.
Referring to FIGS. 1 and 2, a pinning layer 12, a pinned layer 13, a dielectric layer 14, and a free layer 15 are sequentially formed over a first electrode 11. The pinning layer 12, the pinned layer 13, and the free layer 15 are formed of metal compounds.
Then, a second electrode 16 is formed over the free layer 15. Using the second electrode 16 as an etch barrier, the free layer 15, the dielectric layer 14, the pinned layer 13 and the pinning layer 12 are sequentially etched to form an MTJ cell. Here, the free layer 15 and the pinned layer 13 should be separated electrically by the dielectric layer 14 so that the MTJ cell operates normally.
However, the typical method for forming the MTJ cell may produce a conductive etch byproduct during etching, as represented by circle “A” in FIGS. 1 and 2, thereby deteriorating the electrical properties of the MTJ cell. The metal compounds forming the pinning layer 12, the pinned layer 13 and the free layer 15 have high boiling points. Accordingly, the conductive etch by product 18 produced during the etching of the metal compounds is evaporated, but redeposited on the side wall of the MTJ cell. The conductive etch byproduct 18 redeposited on a sidewall of an MTJ portion 17 can short the pinned layer 13 and the free layer 15, deteriorating the electrical properties of the MTJ cell. This may cause a fail in a semiconductor device, such as an MRAM, to which the MTJ cell is applied, decreasing reliability and manufacturing yield of the semiconductor device. The conductive etch byproduct 18 deposited on the sidewall of the MTJ portion 17 is produced during the etching of the pinning layer 12. Accordingly, there is a need for a method for preventing the deterioration of the electric property of the MTJ cell caused by the conductive etch byproduct 18.